The present invention generally relates to an electrochemical cell and, more particularly, relates to an electrochemical cell having increased anode-to-cathode interface area.
Electrochemical cells are commonly employed to supply voltage for electrically operated devices, particularly for portable electrically operated devices. Currently, the popular alkaline cells of the generally cylindrical type are commercially available in industry standard sizes including D-, C-, AA-, AAA-, and AAAA-size cells, as well as other sizes and configurations. Electrochemical cells, such as the aforementioned type, commonly provide a predetermined open circuit voltage supply.
Conventional cylindrical alkaline cells generally have a cylindrical-shaped steel can provided with a positive cover at one end and a negative cover at the opposite end. The cylindrical cell has a positive electrode, commonly referred to as the cathode, which is often formed of a mixture of manganese dioxide, graphite, potassium hydroxide solution, deionized water, and a TEFLON.RTM. solution formed about the interior side surface of the cylindrical steel can. A cup-shaped separator is generally centrally disposed in an inner cylindrical volume of the can about the interior surface of the cathode. A negative electrode, commonly referred to as the anode, is typically formed of zinc powder, a gelling agent, and other additives, and is disposed along with an electrolyte solution within the separator. One example of a conventional cylindrical cell is disclosed in U.S. Pat. No. 5,501,924, which is hereby incorporated by reference.
Conventional cells of the aforementioned cylindrical type commonly have a single anode and a single cathode contained within the steel can with the separator interfaced therebetween. Usually, the cathode is disposed adjacent the inner wall of the steel can, while the anode is disposed within a cylindrical volume defined by the cathode. Accordingly, the separator has an anode-to-cathode interface area generally defined by the shape and size of the anode and cathode. With the conventional cell, the anode-to-cathode interface area is approximately equal to the surface area of the periphery of the cylindrical anode. In addition, the anode is generally provided in the shape of a cylinder with a uniformly curved outer surface parallel to the container wall such that the cathode is not easily susceptible to breakage which can lead to ionic and electric discontinuity within the cell.
A primary goal in designing alkaline cells is to increase the service performance which is the length of time for the cell to discharge under a given load to a specific voltage at which the cell is no longer useful for its intended purpose. Commercially available alkaline cells commonly have an external size that is defined by industry standards, thereby limiting the ability to increase the amount of active cell materials that can be utilized. Yet, the need to find new ways to increase service performance remains the goal of the cell designers.